IV CONTENTS OF VOL. XLVII. FOURTH SERIES. 



Page 

 Mr. B. Moon's Eeniarks on the Analytical Principles of Hy- 

 drodynamics, in Beply to Professor Challis 143 



Dr. Helrnholtz on Galvanic Polarization in Liquids free from 



Gas 145 



Notices respecting New Books : — 



Mr. W. T. Pierce's Treatise on Practical Solid or Descrip- 

 tive Geometry : embracing Orthographic Projection and 



Perspective or Badial Projection , 153 



Prof. M. Tarnall's Catalogue of Stars observed at the 

 United States Naval Observatory during the years 1845 



to 1871 155 



On a new Determination of the Mechanical Equivalent of Heat, 



by H. Serrano y Eatigati 155 



On the Expansibility of Ebonite by Heat, by P. Kohlrausch. . 156 

 On the Discharge of Electrified Conductors, by J. Moutier . . 157 



NUMBEB CCCXL— MAECH. 



The Earl of Eosse on the Electric Eesistance of Selenium . . 161 

 Mr. J. A. Phillips on the Composition of certain Mine Waters. 164 

 Mr. J. Croll on the Physical Cause of Ocean-currents. (With 



a Plate.) 168 



M. H. Herwig on the Number and Weight of the Molecules 



of iEther contained in Electric Conductors 190 



Lord Eayleigh on the Manufacture and Theory of Diffraction- 

 gratings. . . , . 193 



M. J. L. Soret on some Phenomena of Polarization by Diffusion 



of Light 205 



M. A. Terquem on the Transformation of the Vibroscope into 

 a Tonometer, and its employment for the Determination of 



the Absolute Number of Vibrations 212 



Notices respecting New Books : — 



The Eev. S. Hawtrey's Introduction to the Elements of 



Euclid 215 



Proceedings of the Eoyal Society : — 



Lieut. Sale on the Action of Light on the Electrical Ee- 

 sistance of Selenium 216 



Mr. D. M'Kichan's Determination of the Number of 



Electrostatic Units in the Electromagnetic Unit .... 218 

 Messrs. Stewart and Tait on the Heating of a Di«k by 



rapid Eotation in vacuo 219 



Mr. P. Chambers on the Diurnal Variations of the Wind 



and Barometric Pressure at Bombay 228 



Proceedings of the Geological Society : — 



Dr. J. Bryce on the Jurassic Eocks of Skye and Eaasay. 229 

 Mr. D. Mackintosh on the more remarkable Boulders of 

 the North-west of England and the Welsh Borders . . 230 



